Many of the lasers that are used in healthcare, medical or bio-technology applications operated on the basis of absorption of the light in water. However, since water pervades most biological tissue, the medical lasers tend not to be selective to a particular tissue type. During medical procedures using such non-selective lasers, there can be additional risk and complications from unwanted collateral damage. Also, for laser wavelengths that are significantly absorbed by water, the light may not penetrate very far into the tissue. Consequently, lasers tend to treat only the surface of the tissue exposed to the light. Therefore, there exists a need for lasers and procedures based on light sources or lasers that can be selective and that can penetrate deeper into tissue.
Mid-infrared lasers, such as lasers that operate between approximately 1 and 10 microns, preferably between 1.2 and 4.5 microns, can be implemented that operate near absorption peaks of various tissues, such as adipose (e.g., fat, cholesterol, lipids), collagen and elastin. Moreover, the wavelength of the lasers can be selected to minimize water absorption and scattering through tissue. Thus, mid-infrared lasers tuned to optical absorption in particular tissue constituents can be used in one embodiment for selective damage in therapeutic procedures. In another embodiment, the optical absorption or reflection spectroscopy can be used as a diagnostic technique to differentiate between different tissue types. Moreover, by operating at mid-infrared wavelengths with less water absorption and tissue scattering, the penetration depth for the light can be increased to several millimeters, as an example. These features of mid-infrared light can be beneficial in a number of medical fields, including but not limited to ophthalmology, dermatology, cardiology and neurology as well as treatment of type 2 diabetes and other ailments associated with obesity.
The following U.S. patent references are related to at least one example embodiment of the present invention: U.S. Pat. Nos. 5,618,284; 5,779,696, 6,159,205; 6,251,103; 6,605,080; 6,986,764; 7,060,061; 7,633,673; 2008/0015557; 2009/0028193; and 2009/0054879.